Steerable catheter guidewire

ABSTRACT

Steerable flexible elongate device (16) comprising a flexible elongate member (26) having proximal distal extremities (17,18) and having a centrally disposed lumen (29) extending into the distal extremity (18). The flexible elongate member (26) has at least three additional lumens (31,32,33) spaced apart circumferentially about the centrally disposed lumen (29) and extending into the distal extremity (18). A stiffener element (36) is disposed in the centrally disposed lumen (29) and has proximal and distal extremities (38,39). Additional flexible elongate elements (41,42,43) having a negative coefficient of expansion are disposed in each of the three additional lumens (31,32,33) and have proximal and distal extremities. The distal extremities of the stiffener element (36) and the additional flexible elongate elements (41,42,43) are secured to the distal extremity (18) of the flexible elongate member (26). The proximal extremities of the stiffener element (36) and the additional flexible elongate elements (41,42,43) are also secured relative to the distal extremity (18) of the flexible elongate member (26). &lt;IMAGE&gt;

This invention relates to a flexible elongate device having a steerabledistal extremity and an apparatus for use therewith and method and moreparticularly to such a device which can be in the form of a steerableguide wire or a steerable catheter.

Steerable catheters and the guide wires have heretofore been provided,however, the steerability of the distal extremities of these guide wiresand catheters has been very limited and difficult to control. There istherefore a need for a new and improved and flexible elongate devicewhich can be in the form of a guide wire or catheter which hasexceptional steerability characteristics at its distal extremities.

In general, it is obvious that the present invention is to provide aflexible elongate device having a steerable distal extremity and anapparatus for use therewith and a method.

Another object of the invention is to provide a device of the abovecharacter which can be in the form of a guide wire.

Another object of the invention is to provide a device of the abovecharacter which can be in the form of a catheter.

Another object of the invention is to provide a device of the abovecharacter in which the catheter can be a balloon dilatation catheter.

Another object of the invention is to provide a device of the characterin which the steering of the distal extremity can be controlled by theuse of a joystick and in which the distal extremity follows themovements of the joystick.

Another object of the invention is to provide a device of the abovecharacter in which a stiffening wire is utilized.

Another object of the invention is to provide a device of the abovecharacter in which the stiffening wire is provided with one or morehinge points in its distal extremity to make possible different types ofbends in the distal extremity of the device.

Another object of the invention is to provide a device of the abovecharacter in which the bend in the distal extremity is proportional tothe movement of the joystick.

Another object of the invention is to provide a device of the abovecharacter in which the bending of the distal extremity is achieved bythe use of shape memory wires having a negative coefficient ofresistance.

Another object of the invention is to provide a device of the abovecharacter in which the changes in the negative resistance of the wiresare measured to predict the amount of movement of the distal extremityof the device.

Another object of the invention is to provide a device of the abovecharacter in which compensation is provided for differences in thenegative coefficient of resistance in the shape memory wires of adevice.

Another object of the invention is to provide a device of the abovecharacter in which the amount of bending of the distal extremity iscontrolled in accordance with the movement of the joystick.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin conjunction with the accompanying drawings.

FIG. 1 is a side elevational view of a flexible elongate device having asteerable distal extremity incorporating the present invention andconnected to a joystick control apparatus for controlling the same.

FIG. 1A is a side elevational view of another embodiment of a deviceincorporating the present invention.

FIG. 2 is an enlarged detail view of the distal extremity of theflexible elongate device shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 2.

FIG. 5 is a greatly enlarged cross-sectional view of a portion of theflexible elongate device shown in FIG. 2.

FIG. 6 is a block diagram showing the electronics for providingelectronically steerable distal extremities for a flexible elongatedevice in the form of either a guide wire or catheter.

FIG. 7 is a graph showing the resistance characteristics of the wiresutilized in the flexible elongate device of the present invention.

FIG. 8 is a partial side elevational view showing a flexible elongatedevice in the form of a guide wire and showing a bend which can beformed in the distal extremity thereof.

FIG. 9 is a cross-sectional view similar to FIG. 3, showing anotherembodiment of the present invention utilizing additional lumens.

FIG. 10 is a side elevational view of the flexible elongate device inthe form of a guide wire in which the distal extremity is bent into acompound bend.

FIG. 11 is a partial cross-sectional view showing a flexible elongatedevice incorporating another embodiment of the invention in the form ofa balloon dilatation catheter.

FIG. 12 is a cross-sectional view taken along the line 12--12 of FIG.11.

In general, the steerable flexible elongate device incorporating thepresent invention is comprised of a flexible elongate member havingproximal and distal extremities. The flexible elongate member isprovided with a centrally disposed lumen extending into the distalextremity thereof and at least three additional lumens spaced apartcircumferentially about the centrally disposed lumen and extending intothe distal extremity of the flexible elongate member. A stiffening wireis disposed in the central lumen and has proximal and distalextremities. Means is provided for securing the distal extremity of thestiffening wire to the distal extremity of the flexible elongate memberand for securing the proximal extremity of the stiffening wire to theproximal extremity of the flexible elongate member. Additional flexibleelongate shape memory wires having a negative coefficient of resistanceare disposed in each of the three additional lumens and have proximaland distal extremities. Means is provided for securing the proximal anddistal extremities of the additional flexible elongate elements to theproximal and distal extremities of the flexible elongate member.

More in particular, the steerable flexible elongate device 16 isprovided with proximal and distal extremities 17 and 18 and has itsproximal extremity 17 mounted in a connector 19. The connector 19 isconnected to a cable 21 which is connected to another connector 22mounted in a control console 23 having a pivotally mounted joystick 24thereon. The joystick 24 is movable from a normal position to variouspositions within a cone having a center axis extending along thedirection of the joystick 24 to cause movement of the distal extremityor tip 18 of the device 16 in accordance with the movement of thejoystick 24 as hereinafter described.

The flexible elongate device 16 in FIGS. 1 and 2 is shown in the form ofa guide wire, the distal extremity or tip 18 of which is shown inenlarged cross-sectional form in FIG. 2. The distal extremity 18 iscomprised of flexible elongate member 26 formed of a suitable plasticsuch as polyethylene, polyamide or silicone. It can be cylindrical inform and has proximal and distal extremities 27 and 28. The flexibleelongate member 26 is provided with a centrally disposed lumen 29 whichextends substantially the entire length of the member 26 to the distalextremity 28. The centrally disposed lumen 29 can have a suitable sizeas for example, from 0.002" to 0.010" and preferably a diameter ofapproximately 0.004". The flexible elongate member 26 is provided withat least three additional lumens 31, 32 and 33 which are spaced apartcircumferentially about the centrally disposed lumen 27 and which alsoextend through the length of the flexible elongate member 26. They canhave a suitable size as for example, ranging from 0.0015" to 0.004" andpreferably a diameter of 0.0025". With such sizing of the lumens 27, 31,32, 33 it can be seen that the overall diameter of the flexible elongatemember 26 can be 0.010" or less so that it provides a relatively smalldimension in cross-section while still at the same time providing a webor wall extending between the lumens which is at least 0.0005" in wallthickness.

The flexible elongate member 26 when formed of a polyamide has very gooddesirable mechanical characteristics as for example, good strength aswell as good temperature characteristics, i.e., the capability towithstand temperatures in the range of 70° C. to 120° C. By utilizingthe smallest dimensions, it is possible to provide a flexible elongatemember 26 in the form of a guide wire having an overall diameter rangingfrom 0.008" to 0.010".

In accordance with the present invention a stiffener element or wire 36formed of a suitable material such as stainless steel is disposed in thecentral lumen 27. The stiffener wire 36 should be sized so it isslightly smaller than the lumen in which it is disposed. Thus for alumen of 0.004" in diameter, a stiffener wire of a diameter 0.003" canbe utilized which has a distal extremity 37 and a proximal extremity 38.

Three additional flexible elongate elements or wires 41, 42, 43 areprovided in the three lumens 31, 32, 33. The wires 41, 42, 43 are formedof a material which has a negative coefficient of expansion for purposeshereinafter described. The size of the wires 41, 42 and 43 is selectedin accordance with the pulling force which is to be generated by thewires as hereinafter described. The wires 41, 42, 43 have distalextremities 44 and proximal extremities 46. In the embodiment shown inFIGS. 2 and 3 and in which lumens 31, 32 and 33 are provided having adiameter of 0.0025", the wires 41, 42 and 43 can have a diameter of0.002". For the other sizes of lumens, wires having diameters rangingfrom 0.001" to 0.010" can be utilized. One type of wire having asuitable negative coefficient of expansion is a nickel-titanium alloymanufactured and sold under the trademark Nitinol. The heating of theNitinol wire changes its crystalline structure causing it to shortenitself or in other words to have a negative coefficient of expansion. Ashereinafter described, the wires 41, 42, 43 serve as electricalconductors for electric current and have their distal extremities 44connected to the distal extremity 37 of the stiffener wire 36 by asuitable means such as solder 47 or by spot welding so that thestiffener wire 36 can serve as a return conductor or a ground return. Arounded tip 48 is provided at the distal extremity 28 of the tubularmember 26 and can be formed of a suitable material such as a conductiveepoxy to augment the electrical connection between the wires 41, 42 and43 and the ground return wire 36.

If desired, the stiffener wire 36 can be provided with one or more hingepoints to facilitate the forming of bends having predeterminedconfirmations in the distal extremity of the device 16. Thus as shown inFIG. 2, hinge points have been provided which are spaced at variousdistances from the distal extremity 37 of the stiffener wire 36. Thesehinge points have been provided by forming annular grooves or recessesof various lengths. Thus by way of example, with a stiffener wire 36 ofa diameter of 0.003", the annular grooves or recesses can be formed to adepth of 0.0005" so that the remaining portions of the stiffening wirewithin the grooves have a thickness of 0.002". The grooves or recesses52, 52 and 53 can have various lengths extending along the axis of thestiffener wire 36 as for example, ranging from 0.0001" to 0.020" andvarious depths. With a single hinge point in the guide wire 36 it ispossible to achieve a bend such as shown in FIG. 8 in all 360° inrotation.

It should be appreciated that different diameters on the stiffener wirecan be provided to form hinge points in various manners. For example,the annular grooves or recesses can be formed by machining or grinding.They also can be formed by etching to reduce the diameter.Alternatively, the lengths of the stiffener wire between the hingepoints can be increased in diameter by electroplating those annularregions by a suitable material such as nickel or chromium.Alternatively, those annular regions can be enamel coated.

The proximal extremity 27 of the flexible elongate member 26 is securedto another flexible elongate member 56 having proximal and distalextremities 57 and 58. The flexible elongate member 56 is provided witha single lumen 59 into which the proximal extremity 27 of the flexibleelongate member 26 extends (FIG. 2) and is bonded therein by suitablemeans such as an adhesive or epoxy. The flexible elongate member 56 isalso formed of a suitable plastic such as a polyamide although less heatsensitive materials such as polyethylene can be utilized since theNitinol wires 41, 42 and 43 are not in contact with the same.

The connection between the distal extremity 58 of the flexible elongatemember 56 and the proximal extremity 27 of the flexible elongate member26 is shown in detail in FIG. 5. Electrical conductors 61, 62, 63 areprovided in the form of enameled copper wire which are bonded to theNitinol wires 41, 42, 43 respectively by suitable means such as spotwelded joints 64 and by providing an epoxy 66 which surrounds the joints64. It should be noted that the spot weld joints 64 are offsetlongitudinally of the axis of the flexible elongate device 16 tofacilitate making the spot weld joints 64 and also to prevent shortingof one spot weld joint to another. A support wire or core wire 68 isprovided within the lumen 59 and is secured to the proximal extremity ofthe stiffener wire 36 by a spot weld joint 69. The support wire 68 canhave the same size or a greater size than the stiffener wire 36 toprovide the desired amount of rigidity in the flexible elongate device16.

The conductors 61, 62, 63 and the support wire 68 extend to the proximalextremity 57 of the flexible elongate member 56 and also to the proximalextremity of the flexible elongate device 16 and are electricallyconnected to slip rings 71, 72, 73 and 74 mounted on the proximalextremity 57 and connected respectively to the conductors 61, 62 and 63and to the support wire 68 to make electrical connections therewith.These slip rings 71, 72, 73, 74 are adapted to engage sleeves 76, 77, 78and 79 respectively provided in the connector 19. These sleeves areconnected by electrical conductors (not shown) provided in the cable 21connected to the connector 22 mounted on the control console 23.

The joystick 24 controls electronic circuitry of the type shown in FIG.6 which is mounted within the control console 23. The positioning of thejoystick 24 controls the position of three wipers 86 which areassociated with three potentiometers R1, R2, and R3. It has been foundthat by the use of the three potentiometers spaced 120° apart of theaxis of the joystick 24, it is possible to precisely position the distalextremity 18 of the flexible elongate device 16 in accordance with thepositioning of the joystick throughout all 360° of rotation within thecone in which the joystick can travel. The common points of theresistors R1, R2 and R3 of the three potentiometers are connected toground as shown. Supply currents are supplied to the potentiometers R1,R2 and R3 through resistors R4, R5 and R6 from voltage reference sourcesidentified as V_(ref). The junctions 88 between these pairs of resistorsprovide analog signals in accordance with the position of the joystick24 to an analog-to-digital converter 91 which by way of example can be asix-channel (A/D) converter. The output of the A/D converter 91 issupplied to a microprocessor 92. The Nitinol wires 41, 42 and 43 arerepresented schematically on the block diagram in FIG. 6 as resistorelements R7, R8, and R9 respectively in which the common points arejoined together and connected to ground as shown, the ground is providedby the connections of the distal extremities of the wires 41, 42 and 43to the distal extremity of the stiffener wire 36 as hereinbeforedescribed so that the wire 36 serves as a ground return as hereinbeforedescribed.

The microprocessor 92, which is connected to the Nitinol wires 41, 42and 43 as represented by the resistors R7, R8, R9, is utilized forpredicting the position of the distal extremity 18 of the flexibleelongate device 16 with respect to a certain position of the joystick24. Let it be assumed that the cone angle for the joystick 24 is 60° andthat the joystick has been moved through one-half of the cone angle, asfor example 30°, to achieve a bend in the distal extremity 18, which isone-half of the total bend which can be achieved. The desired bend isachieved by the passing current through one or more of the Nitinol wires41, 42 and 43 to cause them to contract because of their negativecoefficient of expansion to achieve bends in the distal extremity 18 asshown in dotted lines in FIG. 1.

The shrinkage or contraction of the Nitinol wire with temperature isshown in FIG. 7. The Nitinol wires tested had a three-inch length and adiameter of 2 mils (0.002"). The straight lines 96, 97 and 98 in thegraph in FIG. 7 shows the amount of shrinkage for three such wires as apercent of total length for a temperature ranging from 50° C. to 70° C.and with a resistance ranging from 45 to 55 ohms. It can be seen thatthe shrinkage is linear from the long relatively straight lines 96, 97and 98. It is this linear shrinkage characteristic which is utilized inthe present invention.

Since the amount of bending of the distal extremity of the flexibleelongate device 16 is predicated upon the amount of heating of theNitinol wire, the resistance of the wire is measured to correlate thatshrinkage with the movement of the joystick 24 and the bending of thedistal extremity of the flexible elongate device 16. For that purpose,an RF source 101 of a high frequency ranging from 20 to 30 kHz at aconstant current, as for example 50 microamperes, is used. This value ofcurrent is small enough so that it will not have any substantial effecton heating up of the Nitinol wire while still giving a meaningful signalwhich can be sensed by the microprocessor 92 to measure the resistanceof the wires 41, 42 and 43. The AC signals produced represent themeasured resistances of the Nitinol wires 41, 42 and 43 represented bythe resistors R7, R8 and R9 in FIG. 6 are supplied through a narrow bandfilter 102 and an amplifier 103 to the input of a six-channel A/Dconverter 91. The microprocessor 92 samples the outputs from theamplifiers 103 which represent the changes of the position of thejoystick 24 as the wiper 86 moves with respect to the associatedpotentiometers R1, R2 and R3. The microprocessor 92 ascertains whatresistance should be found in the Nitinol wire associated with thatresistor in accordance with the parameters provided by the graph shownin FIG. 7. The graph in FIG. 7 can be in the form of a lookup table inthe microprocessor 92 or alternatively a formula in the microprocessor92. The microprocessor 92 using this information turns on a switch whichis identified as transistor Q1 for the resistor R7, Q2 for the resistorR8, and Q3 for the resistor R9 to allow the application of current froma constant current source 106, as for example, one providing a constantcurrent of 50 milliamperes. The microprocessor 92 turns the transistorsQ1, Q2 and Q3 on and off to provide a pulse width modulated signalcreating a current signal, the duty cycle of which is controlled and isproportional to the resistance which it is desired to be achieved forthat Nitinol wire. Since this resistance is being constantly sampled bythe microprocessor 92, it is possible to precisely position the distalextremity of the flexible elongate device 16 and to stop the applicationof current when the desired bend has been reached in the distalextremity 18. If the Nitinol wire begins to cool down, this will also besensed by the microprocessor 92 and additional current is supplied tothe Nitinol wire to maintain it in a position in accordance with theposition of the joystick 24. It is possible to provide a criticallydamped system so there is no undershoot or overshoot even though theremay be some heat loss into the blood pool in which the device isdisposed. By the use of a single joy stick 24 a simple bend such asshown in FIG. 18 can be provided in the distal extremity 18 of thecatheter 16.

In order to achieve more complex or compound bends in the distalextremity 18 of the catheter device 16, additional hinge points can beprovided as shown in FIG. 2. The bends can be achieved by providingadditional Nitinol pull wires and additional lumens such as shown inFIG. 9. As shown therein, the separate flexible elongate tubular member111 is provided with a centrally disposed lumen 112 through which astiffener wire 113 extends. A plurality of additional flexible elongatetubular members 114 are provided which have lumens 116 extendingtherethrough. By way of example as shown in FIG. 9, six of such flexibleelongate members 114 can be provided and can be bonded around the outercircumference of the flexible elongate tubular member 111 by suitablemeans such an adhesive 115 to provide a unitary flexible elongatetubular assembly 117. Alternatively, the assembly can be mounted withinanother thin-walled tube (not shown). With such assemblies, a set ofthree pull wires each can be provided with the pull wires being spacedapart 120° circumferentially of the stiffener wire 113. Thus wires 121,122 and 123 constitute one set of pull wires, and wires 126, 127, 128constitute another set of pull wires. One set of these wires isconnected to the stiffener wire 113 just distal of one of the hingepoints about which it is desired to form a bend and the second set ofNitinol pull wires is attached just distal of another hinge point in thestiffener wire to cause bending around that hinge point. The two sets ofpull wires are connected to two separate joysticks and the associatedelectronics of the type hereinbefore described to make it possible tocreate bending at two different hinge points to create a compound bendin the distal extremity 18 of the catheter device 16 such as that shownin FIG. 10.

From the foregoing it can be seen that the flexible elongate devicehaving a steerable distal extremity of the present invention and theapparatus for use therewith and the method employed have manyapplications. They can be utilized for entering vessels in the humanbody for diagnostic and therapeutic purposes. For example, the coronaryarteries and other coronary vessels of the heart can be readilynavigated by the utilization of the joystick control, the position ofwhich can be observed to guide the progress of the flexible elongatedevice as it is advanced into the vessels of the patient. Also, thedistal extremity of the device can be observed fluoroscopically by theuse of radiopaque markers (not shown) provided on the distal extremityof the device. By moving the joystick in the direction in which thedistal extremity of the flexible elongate device is to extend, thedevice can be advanced through tortuous vessels with relative ease. Therelatively small amount of heat which is created by the Nitinol wires toachieve the desired bending is readily dissipated by the blood flowingin the vessel of the patient without danger to the patient. Because ofthe microprocessor control utilized, it is possible for the physician oroperator to position the joystick in a desired position and know thatthe distal extremity of the flexible elongate device will bend inaccordance with the position of the joystick.

Although the foregoing description has been primarily in conjunctionwith a flexible elongate device in the form of a guide wire, it shouldbe appreciated that the principles as set forth are applicable to manyother types of elongate flexible devices, such as to guiding catheters,balloon dilatation catheters and the like, particularly when they are tobe used to navigate tortuous vessels which are difficult to enter withconventional steerable guide wires and catheters.

The use of the present invention in conjunction with a steerable balloondilatation catheter 31 is shown in FIGS. 11 and 12. It consists of aflexible elongate member 132 formed of a suitable plastic ashereinbefore described and which is provided with a centrally disposedlumen 133 having a stiffener wire 134 extending therethrough. It is alsoprovided with at least three lumens 136 which are spacedcircumferentially around the lumen 133 as for example, 120° apart fromeach other and have disposed therein Nitinol pull wires 137. Theelongate member 132 is provided with a distal extremity 138.

Another elongate coaxial tubular member 141 is provided which has alumen 142 therein through which the flexible elongate member 132extends. The flexible elongate member 141 can be formed of a suitablematerial as for example, a heat shrinkable plastic. An inflatableballoon 146 is provided on the distal extremity of the flexible elongatemember 141 and can be formed integral therewith or it can be formed as aseparate balloon secured by an adhesive to the flexible elongate member141. In FIG. 11, the balloon is shown being formed integral with theflexible elongate member 141 and has a distal extremity 147 bonded tothe distal extremity of the flexible elongate member 132 by suitablemeans such as an adhesive 148.

As can be seen in FIG. 11, the balloon 146 is provided proximal of thedistal extremity 138 of the flexible elongate member 132 so that thedistal extremity of the flexible elongate member 132 can serve as afixed guide wire for steering of the balloon dilatation catheter 131.The distal extremity 138 of the flexible elongate member 132 can beformed into a bend as shown by dotted lines by use of a joystick of thetype hereinbefore described to facilitate advancing the balloondilatation catheter 131 into tortuous vessels in the patient as forexample, in the heart of the patient. Radiopaque markers 151 can beprovided within the balloon on the flexible elongate member 132 tofacilitate observing the positioning of the balloon in the vessel of thepatient under X-ray fluoroscopy. When the balloon is in the desiredposition, the balloon 146 can be inflated by the introduction of liquidor a suitable gas through the balloon inflation lumen 142 to perform anangioplasty. After the angioplasty has been completed the balloon 146can be deflated and the catheter 131 removed in a conventional manner.

As hereinbefore described and as shown in FIG. 7 in connection with thepresent invention, it has been found that different pieces of Nitinolwire may have different negative coefficients of expansion, even whentaken from the same roll of wire. These typical differences are shown bythe three straight lines 96, 97 and 98 in FIG. 7 which differences mayrepresent several percent. In certain applications, it has been founddesirable to compensate for these differences so that the joystickcontrol as hereinbefore disclosed can provide precise control of distalextremity of the elongate device which it is intended to manuever. Inorder to accomplish this, a module 161 is provided into which theproximal extremity 17 of the flexible elongate device 16 is connected asshown in FIG. 1A. The module 161 includes a termination 162 which isprovided with a plurality of male connectors mounted thereon which areadapted to be received by female connectors 164 provided in a connectorblock 166 that is connected to the cable 21. Cable 21 is connected tothe control console 23 in the same manner as the cable 21 in FIG. 1. Theconductors 61, 62 and 63 and the connector 68 are connected to the maleterminals 163. A serial PROM or EEPROM 171 is provided within the module161 and is connected by conductors 172 to additional male terminals 163.The EEPROM 171 is connected into the microprocessor 92 as shown in FIG.6.

Operation and use of the serial PROM or the EEPROM 171 to compensate forthe differences in the negative coefficients of expansion of the Nitinolwires 41, 42 and 43 can now be briefly described as follows. As soon asthe elongate tubular device 16 has been manufactured as hereinbeforedescribed, the distal extremity 18 is placed in the constant temperaturebath, as for example, at a body temperature of 96.8° F. It is thereafterplaced in another bath at a different temperature as for example at anelevated temperature 125° F. At each of these temperatures theresistance values of the three Nitinol wires 41, 42 and 43 are measuredand recorded in the EEPROM 171. This information in the EEPROM 171 isavailable to the microprocessor 92 as shown in FIG. 6 and is utilizedfor making compensations so that for each incremental movement in anydirection the joystick 24 is moved, the distal extremity 18 of thedevice 16 is moved the same incremental amount regardless of whichNitinol wire ie engaged. Thus, the microprocessor 92 using theresistance information stored in the EEPROM 171 compensates for anydifferences in the negative coefficients of expansion of the threeNitinol wires 41, 42 and 43.

Since the EEPROM 171 has been incorporated into the device 16 itself,the device 16 after manufacture will have information contained inEEPROM 171 for any variances in the negative coefficients of expansionin the Nitinol wires of the device so that it is unnecessary for theuser of the same to make any further adjustments to accommodate any ofthe variances in the negative coefficients of expansion of the wires.

It should be appreciated that rather than producing analog signals fromthe joystick movement, it is possible to provide an optical joystickwhich would provide pulses giving a digital output rather than an analogoutput. For example, this can be accomplished by utilizing a rotatingwheel having holes in it to make and break an optical link to providedigital light pulses which can be sensed electrically.

From the foregoing it can be seen that the present invention hasexcellent capabilities for the precise positioning of the distalextremities of flexible elongate elements or devices from remotelocations under the control of a joystick to permit movement and to formbends in the distal extremity of the device throughout the entire 360°of rotation. The joystick control utilized makes it possible for thephysician or operator to quickly learn how to precisely control thedistal extremity of the flexible elongate device.

I claim:
 1. A tubular steerable flexible elongate device for enteringthe human body for diagnostic and therapeutic purposes, comprising aflexible elongate tubular member having proximal and distal extremitiesand having a centrally disposed lumen extending into the distalextremity, said flexible elongate tubular member having at least threeadditional spaced apart circumferentially about the centrally disposedlumen and extending into the distal extremity, a stiffener elementdisposed in the centrally disposed lumen and having proximal and distalextremities, a flexible elongate element having a negative coefficientof expansion disposed in each of said at least three additional lumensand having proximal and distal extremities, means for securing thedistal extremity of the stiffener element to the distal extremities ofthe flexible elongate elements and means for securing the proximalextremity of the stiffener element and the proximal extremities of theflexible elongate elements relative to the distal extremity of theflexible elongate member.
 2. A device as in claim 1 wherein the distalextremities of the stiffener element and the additional flexibleelongate elements are electrically connected so that the stiffenerelement can serve as a return connection.
 3. A device as in claim 1wherein said flexible elongate member is provided with a set of threeadditional lumens, a set of three additional flexible elongate elementshaving a negative coefficients of expansion disposed in said of threeadditional lumens, means connecting said set of three additionalflexible elongate elements to the stiffener element.
 4. A device as inclaim 1 wherein said stiffener element is provided with at least oneregion of a smaller cross-section to form a hinge point for a bend to beformed in the distal extremity of the flexible elongate member.
 5. Adevice as in claim 4 wherein said stiffener element is provided with atleast two spaced-apart portions of reduced cross-section to provide atleast two spaced-apart hinge points to make it possible to form acompound bend in the distal extremity of the flexible elongate member.6. A device as in claim 1 together with an additional flexible elongatemember secured to said flexible elongate member and having a lumenextending therethrough, conducting wires extending through said lumen insaid additional flexible elongate member and electrically connected tosaid flexible elongate elements and a support element secured to saidstiffener element and extending through said lumen in said additionalflexible elongate member.
 7. A device as in claim 6 together with aconnector to said additional flexible elongate member and electricallyconnected to said electrical conductors.
 8. A device as in claim 1wherein said additional flexible elongate elements are formed ofNitinol.
 9. A device as in claim 1 together with an additional flexibleelongate tubular member extending over said flexible elongate member, aninflatable balloon carried by the distal extremity of the additionalflexible elongate tubular member, means bonding the distal extremity ofthe balloon to the first named flexible elongate member to provide anairtight seal therebetween in a position proximal of the distalextremity of the first named flexible elongate member so that the distalextremity of the flexible elongate member distal to the balloon can bebent, the additional flexible elongate tubular member and the exteriorof the first named flexible elongate tubular member providing a spaceserving to form a balloon inflation human for inflating and deflatingthe balloon.
 10. A device as in claim 1 together with means carried bythe device for compensating for any differences in the negativecoefficients of expansion of the additional flexible elongate elements.11. A device as in claim 10 wherein said means includes a memory whichhas recorded therein any differences in negative coefficients ofexpansion of the additional flexible elongate elements.
 12. A method forcontrolling the distal extremity of the flexible elongate device formovement in a vessel of a patient in accordance with a pivotally mountedjoystick movable through 360° of rotation in a cone, the distalextremity having therein conductive pull elements with a negativecoefficient of expansion and the flexible member having a centrallydisposed lumen extending into the distal extremity and a stiffenerelement disposed in the centrally disposed lumen, comprising moving thejoystick in a direction within the cone of movement, causing the distalextremity of the flexible elongate member to bend in accordance withmovement of the joystick to facilitate movement of the flexible elongatedevice in the vessel of the patient, measuring the resistance of thepull elements to ascertain the position of the pull elements andsupplying additional current to the pull elements to cause them toassume the desired position with respect to the joystick, the resistanceof the pull elements being sensed by supplying a high frequency radiofrequency of low constant current to the pull elements, sensing theresistance of the pull elements, comparing the resistance of the pullelements with the desired position for the distal extremity of theflexible elongate member and making corrections in the position of thedistal extremity of the flexible elongate member by supplying additionalcurrent to the pull elements in accordance with the sensed resistance ofthe pull elements so that the position of the distal extremity of theflexible elongate member reflects the position of the joystick.
 13. Amethod as in claim 12 together with sensing the resistance of the pullelements at different temperatures to ascertain any differences in thenegative coefficients of expansion of the pull elements and makingcorrections so that upon movement of the joystick, the distal extremityof the flexible elongate device will be moved the same amount for theequivalent movement of the joystick regardless of which pull element isenergized.
 14. In a steerable flexible elongate device, a flexibleelongate member having proximal and distal extremities and having acentrally disposed lumen extending into the distal extremity, saidflexible elongate member having at least three additional lumens spacedapart circumferentially about the centrally disposed lumen and extendinginto the distal extremity, a flexible elongate element having a negativecoefficient of expansion disposed in each of said three additionallumens and having a proximal and a distal extremity, first, second andthird electrical conductors connected to one extremity respectively ofthe flexible elongate elements having a negative coefficient ofexpansion and extending to the proximal extremity of the flexibleelongate member and a common conductor disposed in the centrallydisposed lumen and connected to the other extremity of each of theflexible elongate elements having a negative coefficient of expansionand extending to the proximal extremity of the flexible elongate member,at least a portion of said common conductor serving as a stiffnesselement.